1. Field of the Invention
The invention relates to multipart continuous forms having several plies and a means to securely fasten the plies. More particularly, the invention refers to the use of connecting and locking tabs to secure the plies in a manner which allows for both flexible binding and accurate register.
2. Description of the Prior Art
It is common in the modern business world to use multipart continuous forms which contain a manifold set of plies made from continuous webs or sheets. Such forms are usually stored in zig-zag fashion; contain sprocket holes along their edge so the form can be fed through a feeding mechanism in a business machine, printer, or typewriter; and, might have perforations along one or both edges so that the forms can be easily separated. Some of the forms contain webs of carbonless paper and others use alternate layers of paper and carbon paper. The variety and style of these forms, used in modern business, are many and varied but all have one problem in common. That problem involves the longitudinal shifting of the webs relative to each other. Several attempts have been made to prevent such longitudinal shifting. One method uses lines or dots of adhesive between each ply of the form. This method provides binding which is too rigid; and, because it doesn't have sufficient flexibility, the form "tents" when run through typewriters or computer printers. Another attempted solution uses staples. This method, however, causes damage to the typewriter or printing device. Another approach suggests the use of tongues which are passed through apertures in the inner and outer plays. Although this method provides the necessary flexibility the forms separate easily and are not held together strongly enough to tolerate a bursting operation. A variation of the above method, described in U.S. Pat. No. 3,655,222, glues the tip of the tongue, which passes through the apertures of the inner ply, to the inner side of the remaining outer ply. (The upper and inner plies are made of carbonless copying sheets which can't accept adhesive on their coated exterior sides.) This method provides good flexibility and strength but the inner plies can move relative to the outer plies a distance equal to the width of the aperture hole in the inner plies. This slippage of the inner ply causes it to be out of register with the other inner plies and with both outer plies.
All of the above methods have failed to successfully couple flexible fastening with accurate longitudinal register between the plies.